Press, method for manufacturing the metal plate, method for manufacturing the liquid spray head, method for manufacturing the liquid spray apparatus

ABSTRACT

A pressing apparatus  30  performs plastic working by pressing a punch  36  into a metal plate  31.  The pressing apparatus  30  includes a rough surface part  47  that is formed at a front-end-side area of an outer surface of the punch  36,  the level of surface roughness of the rough surface part  47  being greater than that of other area part, and a smooth surface part  48  that is formed at a base-end-side area that is located at a relatively base-end side in comparison with the area of the rough surface part  47,  the smooth surface part  48  being smoother than the rough surface part  47.  The punch is inserted up to a point where the rough part goes beyond one surface of the metal plate that is opposite to the other surface thereof that is provided at a side at which the insertion of the punch into the metal plate is started. By this means, the formation of a bump on the punched-side surface is prevented.

The entire disclosure of Japanese Patent Application No. 2008-050903, filed Feb. 29, 2008 is incorporated by reference herein.

The entire disclosure of Japanese Patent Application No. 2008-055445, filed Mar. 5, 2008 is incorporated by reference herein.

The entire disclosure of Japanese Patent Application No. 2009-032813, filed Feb. 16, 2009 is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pressing apparatus, a metal plate manufacturing method, a method for manufacturing a liquid spray head, and a method for manufacturing a liquid spray apparatus. In particular, the invention can be suitably applied to the manufacturing of a liquid spray head nozzle plate through which minute through holes are formed.

2. Related-Art Invention

For example, a filter that is used for filtering liquid that flows in a flow channel of a liquid spray head is made of a thin metal plate (e.g., stainless plate) through which a plurality of through holes each having a very small diameter is formed. The liquid spray head discharges liquid that is retained in a pressure chamber from a nozzle opening in the form of a liquid drop by making a pressure change occur in the liquid retained therein. A few examples of methods for forming holes through a metal plate are an etching method and a press working (plastic working) method, the latter of which uses a metal mold.

As an example of the press working method explained above, a method for forming a through hole that functions as a nozzle opening in a final product by pressing a punch into a thin metal plate, which is the raw material of a nozzle plate, from one surface side of the thin metal plate and thereafter by removing a bulged part that is formed at the other surface side of the thin metal plate that is opposite to the one surface side thereof in a subsequent grinding process is proposed in Japanese Unexamined Patent Application Publication No. 2007-137039 (e.g., Patent Document 1).

When a small hole is formed in a thin metal plate by means of the conventional metal plate working method explained above, in some cases, a ring-shaped bump is formed at the peripheral edge of the hole.

The reason why such a ring-shaped peripheral elevation is formed is that, when a punch is pressed into a metal plate and makes its way in the metal plate, a part of metal material that is pressed and thus yields to the punching pressure of the punch moves to the peripheral edge of the hole (which can be called as escape of metal material). In order to remove such a bump, a process of lapping the bulged surface and thereby forming it into a smooth surface is required in the conventional method.

In view of the foregoing, the present invention has been made with an aim to provide a metal plate pressing apparatus, a metal plate manufacturing method, a method for manufacturing a liquid spray head, and a method for manufacturing a liquid spray apparatus that makes it possible to prevent a bump from forming on a punched-side surface.

SUMMARY OF THE INVENTION

In order to achieve the objective described above, a pressing apparatus according to an aspect of the invention, which performs plastic working by pressing a punch into a metal material plate, includes: a rough part that is formed at least at a front-end-side area of an outer surface of the punch that is brought into contact with the metal material plate, the level of surface roughness of the rough part being greater than that of other area part.

With the configuration described above, since the pressing apparatus performs plastic working by pressing a punch into a metal material plate and includes a rough part that is formed at least at a front-end-side area of an outer surface of the punch that is brought into contact with the metal material plate, the level of surface roughness of the rough part being greater than that of other area part, as the punch makes its way in the metal plate, the rough part of the punch causes the punched part of the metal plate (metal material) to move (i.e., be drawn) in the punching direction by a strong frictional force. Consequently, it is possible to ensure that the metal (material) escapes in the punching direction. Therefore, it is possible to avoid the formation of a bump at the peripheral edge of a hole on the punched-side surface of the metal material plate, thereby saving the trouble of removing the bump formed thereon. In addition, it is possible to prevent the degree of circularity of a minute hole from decreasing, which might otherwise occur if the formed bump collapses and becomes deformed under pressure applied by a metal mold or the like.

It is preferable that a pressing apparatus having the configuration described above should further include a smooth part that is formed at a base-end-side area that is located at a relatively base-end side in comparison with the area of the rough part, the smooth part being smoother than the rough part, wherein the diameter of the rough part is not larger than that of the smooth part.

With the configuration described above, since the pressing apparatus further includes a smooth part that is formed at a base-end-side area that is located at a relatively base-end side in comparison with the area of the rough part, the smooth part being smoother than the rough part, wherein the diameter of the rough part is not larger than that of the smooth part, it is possible to use an existing punch just by working the outer surface of the existing punch so as to increase the surface roughness level thereof. In addition, it is possible to easily form the rough part not throughout an outer surface of the punch but only on a surface that is necessary to be subjected to surface roughening.

In the configuration described above, it is preferable that the punch should be inserted up to a point where the rough part goes beyond one surface of the metal material plate that is opposite to the other surface thereof that is provided at a side at which the insertion of the punch into the metal material plate is started.

With the configuration described above, since the punch is inserted up to a point where the rough part goes beyond one surface of the metal material plate that is opposite to the other surface thereof that is provided at a side at which the insertion of the punch into the metal material plate is started, it is less likely that a pattern of streaks (impression) is formed in the metal material plate along the punching direction as the imprinted copy of the rough shape of the rough part within the range of the plate thickness of the metal material plate. In addition, even when such an imprinted pattern is formed therein, it is possible to smooth away the streaks because of smoothening pressure applied by the smooth surface. Thus, the punch-worked surface of the metal material plate is smooth when viewed within the range of the plate thickness of the metal material plate, thereby eliminating a need for another separate process of removing the imprinted copy of the roughness of the rough part within the range of the plate thickness of the metal material plate.

In the configuration described above, it is preferable that the punch should include a straight part that is uniform in outer diameter from the front end of the punch toward the base end thereof; and that the rough part should be formed at least at a front-end-side area of an outer surface of the straight part whereas the smooth part should be formed at a base-end-side area that is located at a relatively base-end side in comparison with the area of the rough part.

The term “uniform” in the outer diameter of the punch means that the diameter is substantially the same throughout it with some allowable margin of error, for example, to the extent of the roughness of the rough part or so.

With the configuration described above, since the punch includes a straight part that is uniform in outer diameter from the front end of the punch toward the base end thereof; and the rough part is formed at least at a front-end-side area of an outer surface of the straight part whereas the smooth part is formed at a base-end-side area that is located at a relatively base-end side in comparison with the area of the rough part, it is possible to ensure that the rough part that is formed on the straight part draws a part of the metal material plate that has been brought into contact with the punch in the punching direction. On the other hand, the smooth surface of the smooth part is copied on a part of the metal material plate that is in contact with the smooth part without being in contact with the rough part. Thus, this part of the metal material plate is formed to be smooth.

In the configuration described above, it is preferable that the punch should include a tapered part that is formed at a relatively base-end side in comparison with the area of the straight part; the diameter of the tapered part should gradually increase from the front-end side toward the base-end side; and the rough part should be formed in the outer surface of the tapered part.

With the configuration described above, since the punch includes a tapered part that is formed at a relatively base-end side in comparison with the area of the straight part; the diameter of the tapered part gradually increases from the front-end side toward the base-end side; and the rough part is formed in the outer surface of the tapered part, when punching pressure is applied to the metal material plate, the rough part presses the material of the metal material plate in the punch-pressing direction and thus prevents the material of the metal material plate from moving toward the punched-side surface. By this means, it is possible to avoid the formation of a bump at the peripheral edge of a hole on the punched-side surface of the metal material plate with greater reliability.

In the configuration described above, the rough part may be pear-peel finished.

A metal plate manufacturing method according to an aspect of the invention is a method for manufacturing a metal plate by forming a hole as a result of pressing a punch into a metal material plate, the metal plate manufacturing method including: a first step of forming a hole by pressing, into the metal material plate, the punch that includes a rough part that is formed at least at a front-end-side area of an outer surface of the punch that is brought into contact with the metal material plate, the level of surface roughness of the rough part being greater than that of other area part.

Since the metal plate manufacturing method includes a first step of forming a hole by pressing, into the metal material plate, the punch that includes a rough part that is formed at least at a front-end-side area of an outer surface of the punch that is brought into contact with the metal material plate, the level of surface roughness of the rough part being greater than that of other area part, as the punch makes its way in the metal plate, the rough part of the punch causes the punched part of the metal plate (metal material), which is pressed and thus yields to the punching pressure of the punch, to move in the punching direction by a strong frictional force. Consequently, it is possible to ensure that the metal (material) escapes in the punching direction. Therefore, it is possible to avoid the formation of a bump at the peripheral edge of a hole, thereby saving the trouble of removing the bump formed thereon, which must be done if a conventional method is used. As a consequence thereof, it is possible to easily manufacture a metal plate in which holes are formed by plastic working. In addition, it is possible to prevent the degree of circularity of a hole from decreasing, which might otherwise occur if the formed bump collapses and becomes deformed under pressure applied by a metal mold or the like.

In the metal plate manufacturing method described above, in the first step, the punch may be inserted up to a point where the rough part goes beyond one surface of the metal material plate that is opposite to the other surface thereof that is provided at a side at which the insertion of the punch into the metal material plate is started.

With the feature described above, in the first step, since the punch is inserted up to a point where the rough part goes beyond one surface of the metal material plate that is opposite to the other surface thereof that is provided at a side at which the insertion of the punch into the metal material plate is started, when the punch is pressed into the metal material plate and makes its way in the metal material plate, the smooth part applies smoothening pressure to the rough surface formed as the imprinted copy of the rough shape of the rough part. Therefore, it is possible to smoothen the inner circumferential surface of a hole that is formed in the metal material plate.

It is preferable that the metal plate manufacturing method described above should further include a second step of removing a bulged part that is formed around the hole formed in the first step on the one surface of the metal material plate that is opposite to the other surface thereof that is provided at the side at which the insertion of the punch into the metal material plate is started.

The metal plate manufacturing method described above further includes a second step of removing a bulged part that is formed around the hole formed in the first step on the one surface of the metal material plate that is opposite to the other surface thereof that is provided at the side at which the insertion of the punch into the metal material plate is started. Therefore, it is possible to form the hole into a through hole by grinding away the bulged part that was formed on the reverse face of the metal material plate. In addition, it is possible to form the thickness of the metal material plate into a predetermined thickness.

The metal plate manufacturing method described above may further include a third step of surface treatment.

With the metal plate manufacturing method described above, when the shape of the rough part of the punch is imprinted on the inner circumferential surface of the hole, during the process of liquid-repellent treatment of the metal material plate, it is possible to make it easier to apply liquid for surface treatment and to perform the surface treatment easily.

A method for manufacturing a liquid spray head according to an aspect of the invention is characterized in that a metal plate that has been worked by means of the metal plate manufacturing method explained above is mounted as a nozzle plate from the hole of which liquid is ejected. A method for manufacturing a liquid spray apparatus according to an aspect of the invention is characterized in that the liquid spray head described above is mounted so as to eject liquid from the liquid spray head.

With the manufacturing methods explained above, since a metal plate through which holes each having high degree of circularity are formed is used as a nozzle plate, it is possible to achieve excellent liquid-traveling performance, that is, the traveling of a liquid drop in air, when the liquid drop is ejected from a nozzle opening.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an essential-part sectional view that illustrates the configuration of a recording head.

FIG. 2 is an exploded perspective view that illustrates the configuration of a fluid channel unit.

FIG. 3 is a sectional view that illustrates a nozzle opening that is formed through a nozzle plate.

FIG. 4 is a sectional view that illustrates the essential part of the configuration of a pressing apparatus according to a first embodiment of the present invention.

FIG. 5 is an enlarged sectional view of the surface of a punch.

FIG. 6 is an essential-part sectional view that illustrates punching work that is performed by the pressing apparatus illustrated in FIG. 4.

FIG. 7 is a sectional view that illustrates a metal plate after the removal of a bulged part thereof.

FIG. 8 is a sectional view that illustrates the essential part of the configuration of a pressing apparatus according to a second embodiment of the present invention.

FIG. 9 is an essential-part sectional view that illustrates punching work that is performed by the pressing apparatus illustrated in FIG. 8.

FIG. 10 is an enlarged sectional view that illustrates punching work according to a third embodiment of the present invention.

FIG. 11 is a sectional view that illustrates a metal plate after the removal of a bulged part thereof.

FIG. 12 is an enlarged sectional view that illustrates punching work according to a fourth embodiment of the present invention.

FIG. 13 is a sectional view that illustrates the essential part of the configuration of a pressing apparatus according to a fifth embodiment of the present invention.

FIG. 14 is a diagram that illustrates the configuration of an ink-jet printer.

1 Recording Head, 10 Nozzle Opening, 13 Nozzle Plate, 30 Pressing Apparatus, 31 Metal Plate, 36 Punch, 40 Hole, 43 Small-diameter Straight Part, 46 Tapered Part, 47 Rough Surface Part, 48 Smooth Surface Part EXPLANATION OF PREFERRED EMBODIMENTS

With reference to the accompanying drawings, the best mode for carrying out the present invention will now be explained below. Although various specific features are explained in the following exemplary embodiments of the present invention in order to disclose preferred modes thereof, the invention should be in no case interpreted to be limited to the specific embodiments described below unless any intention of restriction is explicitly shown. In the following explanation, a nozzle plate that is used in an ink-jet recording head (which is a kind of a liquid spray head and is hereafter simply referred to as recording head 1) mounted on an ink-jet recording apparatus, which is an example of a liquid spray apparatus, is taken as an example of a metal plate, which is a workpiece according to exemplary embodiments of the present invention.

First of all, an explanation is given below of the configuration of the recording head 1.

FIG. 1 is an essential-part sectional view that illustrates the configuration of the recording head 1. In the schematic configuration thereof, the recording head 1 is provided with a filter assembly 5 that includes an ink inlet needle 2, a filter 3, an inlet needle unit 4, and the like, and is further provided with a head unit 9 that includes a head case 6, a vibrator unit 7 that is encased therein, a fluid channel unit 8, and the like. An ink flow channel (which is a kind of a liquid flow channel) that leads from an ink cartridge, which is a kind of a liquid supply source, to a nozzle opening 10 of the fluid channel unit 8 is formed inside the recording head 1.

As illustrated in FIG. 2, the fluid channel unit 8 is bonded to the front-end surface of the case head 6 with a vibration plate 11, a fluid channel formation substrate 12, and a nozzle plate 13 being formed to have a layered structure.

The nozzle plate 13, which is provided at the bottom of the fluid channel unit 8, is a thin metal plate through which the plurality of nozzle openings 10 is formed with the array pattern of a plurality of lines having a pitch corresponding to a dot formation density (e.g., 180 dpi). The nozzle plate 13 according to the present embodiment of the invention is made of a stainless steel plate material (a metal material plate according to an aspect of the present invention). The plurality of lines of the nozzle openings 10 (i.e., the plurality of nozzle lines) is arrayed in the scanning direction of the recording head 1. Each of the plurality of nozzle lines is made up of, for example, one hundred eighty nozzle openings 10. A method for manufacturing the nozzle plate 13 will be explained in detail later. As illustrated in FIG. 3, the nozzle opening 10 according to the present embodiment of the invention is a hole that is formed through the nozzle plate 13 in the thickness direction A of the fluid channel formation substrate 12 and the nozzle plate 13. The nozzle opening 10 is made up of a tapered part 24 and a straight part 25. The diameter of the tapered part 24, which is formed at the fluid-channel-formation-substrate (12) side, decreases gradually. The straight part 25, which has a uniform diameter, is in communication with the minimum-diameter part of the tapered part 24. In FIG. 3, the reference symbol A1 denotes the length of the tapered part 24 when viewed in the axial direction, whereas the reference symbol A2 denotes the length of the straight part 25.

The fluid channel formation substrate 12 is a member that is layered between the nozzle plate 13 and the vibration plate 11. Cavities that include a common ink chamber 15, an ink supply port 16, a pressure chamber 17, and the like are formed inside the fluid channel formation substrate 12. These cavities function as an ink flow passage as a whole. The common ink chamber 15 is a kind of a common liquid chamber. The fluid channel formation substrate 12 is manufactured by, for example, etching a silicon wafer. The nozzle plate 13 and the vibration plate 11 seal the openings of each of the cavities mentioned above.

The vibration plate 11 is a plate member that is provided between the fluid channel formation substrate 12 and the head case 6. The vibration plate 11 is configured as a complex plate having a dual-layer structure, which is made up of a supporting plate 21 that is made of a metal such as a stainless steel or the like and an elastic film 22 that is laminated thereon. An island part 19 is formed at a partial region of the vibration plate 11 that is opposite the pressure chamber 17 by, for example, etching away a part of the supporting plate 21 so as to form a ring-shaped region. The front-end surface of the free end of a piezoelectric vibration element 18 is connected to the island part 19. With such a configuration, this part functions as a diaphragm. That is, the vibration plate 11 is formed so that, as the piezoelectric vibration element 18 operates, the elastic film 22 around the island part 19 deforms elastically. In addition, a part of the vibration plate 11 functions as a compliance part 20, which seals the opening of the common ink chamber 15 of the fluid channel formation substrate 12. A partial region of the vibration plate 11 that functions as the compliance part 20 is made up of the elastic film 22 only after etching away, or removing by means of any alternative method other than etching, a part of the supporting plate 21 as done so for the formation of the diaphragm part described above.

The recording head 1, which has an exemplary configuration explained above, can record an image or the like as follows. Upon the activation of the piezoelectric vibration element 18, a pressure change occurs inside the pressure chamber 17. As a result of the pressure change, ink that flowed from an ink cartridge into the pressure chamber 17 through the ink flow passage and is now retained inside the pressure chamber 17 is discharged from the nozzle opening 10 as an ink drop. The ink drop discharged through the nozzle opening 10 lands on a sheet of recording paper, which is an example of a recording target medium. In this way, the recording head 1 can perform image recording.

Next, with reference to FIGS. 4-7, a method for manufacturing the nozzle plate 13 through the plastic working of a pressing machine 30 according to the present embodiment of the invention is explained below. FIG. 4 is a sectional view that illustrates the essential part of the configuration of the pressing apparatus 30.

In the schematic configuration thereof, the pressing apparatus 30 according to the present embodiment of the invention includes a die 32, a base 33, a pressing board 35, and a punch 36. A metal plate 31 (metal material plate), which is the raw material of the nozzle plate 13, is placed on the die 32. The base 33 is mounted on the lower surface of a ram (which is not illustrated in the drawing). The pressing board 35 is provided under the base 33 with an elastic material 34 such as a spring, elastomer, or the like being provided between the base 33 and the pressing board 35. With such a structure, the pressing board 35 can move upward/downward with respect to the base 33. The punch 36 is provided in a downward orientation with its base end being fixed to the base 33.

For example, the metal plate 31 is a plate that is made of invar alloy and has a thickness of 30-100 μm or so. The invar alloy of the metal plate 31 has substantially the same coefficient of linear expansion as that of the fluid channel formation substrate 12 explained earlier. An example of such alloy is “42 Alloy”. Through the adjustment of the nickel content thereof, the metal plate 31 is formed so as to have a coefficient of linear expansion that is approximately equal to that of the fluid channel formation substrate 12. Therefore, it is possible to prevent the nozzle plate 13 from becoming warped when, after the heat bonding of the fluid channel formation substrate 12 to the metal plate 31 or vice versa with the use of a thermosetting resin having thermo-hardening property or the like at the temperature of 200-300° C., it is cooled down to room temperature, thereby making it further possible to prevent the nozzle plate 13 from coming off the fluid channel formation substrate 12.

The die 32 has punch insertion holes 41 each of which has a diameter that is larger than the diameter of a hole (punch hole) 40 that is to be formed in the metal plate 31. The die 32 functions as a female mold that is provided for the punch 36, which functions as a male mold. A guiding through hole 42 is formed through the pressing board 35. The diameter of the guiding through hole 42 is larger than that of the punch 36. Apart of the punch 36 from the front end thereof to the middle body thereof is inserted through the guiding through hole 42.

The punch 36 has the shape of a pillar. The punch 36 has a punch body part 45 and a tapered part 46. The punch body part 45 of the punch 36 is provided at the base (33) side (base-end side). The tapered part 46 of the punch 36 extends from the front-end part of the punch body 45 thereof. The punch body part 45 has a columnar shape, which is uniform in its outer diameter from the base end thereof to the front end thereof when viewed along the punching direction of the punch 36 (which is shown by an arrow K in FIG. 4). The outer diameter of the punch body part 45 of the punch 36 is 20-30 μm. Roughly speaking, the tapered part 46 has the shape of a truncated cone that has a gentle contour curve in its cross section and has an outer diameter that gradually decreases toward the front end thereof. The front-end part of the tapered part 46 is formed as a small-diameter straight part 43 (which is a kind of a straight part according to an aspect of the present invention). The small-diameter straight part 43 has a columnar shape, which is uniform in its outer diameter from the rear end thereof to the front end thereof when viewed along the punching direction K of the punch 36. The front-end surface of the small-diameter straight part 43 is flat.

A rough surface part 47 (which is a kind of a rough part according to an aspect of the present invention) is formed at least at the front-end-side surface area of the outer surface of the punch 36 that is brought into contact with the metal plate 31. The level of the surface roughness of the rough surface part 47 is greater than that of other area part. That is, the rough surface part 47 is not formed throughout the outer surface of the punch 36 but formed at the front-end-side surface area thereof, which is a part that is brought into contact with the metal plate 31 when the punch 36 is punched into the metal plate 31. The rough surface part 47 according to the present embodiment of the invention, which is illustrated in FIG. 4, is formed throughout the surface areas of the small-diameter straight part 43, the tapered part 46, and the front-end area part of the punch body part 45. For example, the surface roughness Ra of the rough surface part 47 is 0.6 μm or greater. The rough surface part 47 is formed so as to increase a coefficient of friction that works when the punch 36 is punched into the metal plate 31. Any kind of surface treatment may be applied so as to form the rough surface part 47 as long as a frictional force that acts on the metal plate 31 is increased thereby. In the present embodiment of the invention, as illustrated in FIG. 5, a minute uneven pattern is formed in the outer surface of the punch 36 through surface treatment such as arc, blast, etching, or the like, where such minute ruggedness is formed by concaving the outer surface of the punch 36 toward the axial center of the punch 36 at each concavity. Specifically, after the cutting and machining of a round bar steel, which is the material of the punch 36, with the use of a lathe, the circumference surface of the punch 36 is subjected to surface working so that the level of the surface roughness of the contour face of the punch 36 after the surface treatment is greater than the level of the surface roughness of the contour face of the punch 36 immediately after the cutting and machining thereof. As a result, the diameter of the concavity thereof thereafter is smaller than that of the original surface before the working. Therefore, in the configuration of the punch 36 according to the present embodiment of the invention, the diameter of the rough surface part 47 is not larger than that of a smooth surface part 48. Note that shot peening may be used so as to form a so-called pear-peel finished surface, which is a surface on which fine irregularities are formed.

Next, an explanation is given below of a punching process (a first step) that is performed with the use of the pressing machine 30 that has the configuration explained above. It is assumed herein that the die 32 is fixed on a supporting stage of the pressing machine 30 such as a bolster or the like that is not illustrated in the drawing and that the base 33 is mounted on the lower surface of a ram. In addition, it is further assumed herein that all tryout mold adjustments such as the adjustment of the relative positions of the die 32 and the base 33 (punch 36), the adjustment of the bottom dead point of the punch 36, and the like have been completed in advance.

First of all, the metal plate 31 that is made of 42 Alloy or the like is placed on the die 32 at a predetermined set position. Then, with the front end of the punch 36 being oriented toward the metal plate 31, the base 33 is lowered. As a result, as illustrated in FIG. 4, the lower surface of the pressing board 35 is brought into contact with the surface of the metal plate 31. Thereafter, the base 33 is further moved downward against the urging force of the elastic member 34. As the base 33 is further lowered, the front-end part of the punch 36 is pushed into the metal plate 31 as guided through the guiding through hole 42 of the pressing board 35. Thereafter, the punch 36 is further lowered to the bottom dead point. By this means, as illustrated in FIG. 6, a hole 40 that has a mating shape as the counterpart copy of the shape of the punch 36 is formed in the metal plate 31. In this process, as the punch 36 makes its way, the metal material of the punched part of the metal plate 31 that is pressed and thus yields to a punching force of the punch 36 mainly moves (i.e., is drawn) toward the front-end side of the punch 36 in the direction K (i.e., plate thickness direction), which is indicated with an arrow in the drawing. As a result, the most part thereof bulges on the reverse face 31 b of the metal plate 31 so as to form a bump 49. On the other hand, even if the metal plate 31 is made of a relatively soft material such as 42 Alloy or the like, no bulged part is formed on the front face 31 a of the metal plate 31, which is the punched-side surface, unlike conventional art according to which a bulged part is formed also on the front face of a metal plate when a conventional punch (whose surface is not rough) is punched therein.

More specifically, as the punch 36 gradually makes its way deeper into the metal plate 31 from the front face 31 a thereof, the metal material of the front-face (31 a) part (at a side at which the punching insertion of the punch 36 is started) of the metal plate 31 and in the neighborhood thereof is pressed by the rough surface part 47 of the punch 36 and thus yields thereto so as to move in the arrowed direction K as drawn thereby. That is, since the punch 36 moves deeper and deeper into the metal plate 31 while drawing the part of the metal material of the metal plate 31 in the arrowed direction K by the rough surface part 47 thereof, the bulged part 49 only is formed on the reverse face 31 b of the metal plate 31, which is opposite to the front face 31 a thereof, without forming any other bulged part around the punched area on the front face 31 a thereof (that is, no bump is formed at the punched front-face 31 a side).

In this way, the hole 40 that has the same shape as that of the punch 36 is formed in the metal plate 31. Note that the hole 40 illustrated in FIG. 6, which is formed in the metal plate 31, is not a through hole. After the formation of the hole 40, the bulged part 49 is removed in a grinding process, which will be explained later. As a result, the hole 40 is formed into the nozzle opening 10, that is, into a through hole.

After the formation of the funnel-shaped hole 40 in the metal plate 31 through the downward movement of the punch 36 to its bottom dead point, the punch 36 is moved upward. As the base 33 moves upward together with the upward movement of the ram, the pressing board 35 starts to move upward at a point in time that is slightly later than the start of the upward movement of the base 33 due to the returning of the elastic material 34 to its original form. Then, the pressing board 35 comes away from the surface of the metal plate 31 and goes up to its top dead point. In this way, a series of punching operations for one hole ends.

Then, a feeder moves the metal plate 31 by a predetermined pitch for the purpose of carrying out the next punching. After the movement of the metal plate 31, a series of punching operations explained above is performed again so as to form the next hole 40 through the metal plate 31 at the predetermined pitch. Through the repetition of the operations explained above, it is possible to sequentially form the plurality of holes 40 through the metal plate 31 at the predetermined pitch.

After the completion of the punching process, the metal plate 31 is demounted from the pressing machine 30 and then is transported to a grinding machine (which is not shown in the drawing). The grinding machine carries out a bump removal process (a second step) as the next step. In the bump removal process, the bulged part 49, which was formed during the punching process on the reverse face 31 b of the metal plate 31, is ground away. As illustrated in FIG. 7, the bump 49 is removed in this grinding process so as to form the hole 40 into the nozzle opening 10, which is a through hole. In addition, the metal plate 31 is polished so as to make the thickness thereof equal to a predetermined plate thickness. After the bump removal process, a lapping process (processing) is carried out. In the lapping process, a part of the surface of the metal plate 31 that was brought into contact with the rough surface part 47 of the punch 36 (more specifically, a rugged pattern of the inner circumferential surface of the nozzle opening 10 that was formed at the surface area thereof corresponding to the rough surface part 47 of the punch 36 as a result of the imprinting of, that is, as the transferred counterpart copy of, the rugged shape of the rough surface part 47 of the punch 36) is removed. Therefore, even when a pattern of streaks (impression) 50 is formed in the surface of the metal plate 31 along the punching direction that is shown by the arrow K as the imprinted copy of the rugged shape of the rough surface part 47 of the punch 36, the streaks 50 are smoothed away in this process so as to ensure that the inner circumferential surface of the nozzle opening 10 is not rough. In this way, the nozzle plate 13 through which the nozzle openings 10 are formed is manufactured.

As explained above, since the rough surface part 47 whose surface roughness level is greater than that of a base-end-side part of the outer surface of the punch body part 45 is formed in the outer surface of the punch 36 of the pressing machine 30 according to the present embodiment of the invention, as the punch 36 makes its way in the metal plate 31, the rough surface part 47 of the punch 36 causes the punched part of the metal plate 31 (metal material), which is pressed and thus yields to the punching pressure of the punch 36, to move (i.e., be drawn) in the direction K that is indicated with the arrow in the drawing. Consequently, it is possible to ensure that the metal (material) escapes in the arrowed direction K in the punching process. Therefore, it is possible to avoid the formation of a bump at the peripheral edge of the hole 40 on the front face 31 a of the metal plate 31, thereby saving the trouble of removing the bump formed thereon. As a consequence thereof, it is possible to easily manufacture the metal plate 31 in which the minute holes 40 are formed by plastic working. In addition, it is possible to prevent the degree of circularity of the minute hole 40 from decreasing, which might otherwise occur if a bump that was formed at the peripheral edge of the hole 40 on the front face 31 a of the metal plate 31 collapses and becomes deformed under the pressure applied by the pressing board 35.

Moreover, if the metal plate 31 that has been worked by the pressing machine 30 described above is mounted as the nozzle plate 13 of the recording head 1 (a fourth step), it is possible to ensure high degree of circularity of the nozzle opening 10. Because of high degree of roundness of the nozzle opening 10, it is possible to expect an improvement in the characteristics of the traveling of a liquid drop in air when the liquid drop is ejected from the nozzle opening 10.

Next, with reference to FIGS. 8 and 9, an explanation is given below of the punch 36 of the pressing machine 30 according to a second embodiment of the invention. The punch 36 according to the present embodiment of the invention is characterized in that the rough surface part 47 is formed at the front-end-side surface area of a metal-contact part of the outer surface of the punch 36 that is brought into contact with the metal plate 31 when the punch 36 is punched into the metal plate 31. In addition, the punch 36 according to the present embodiment of the invention is characterized in that a smooth surface part 48 (which is a kind of a smooth part according to an aspect of the present invention) that is smoother than the rough surface part 47 is formed at a base-end-side surface area of the metal-contact part of the outer surface of the punch 36 that is located relatively closer to the base end in comparison with the formation area of the front-end-side rough surface part 47. Specifically, the rough surface part 47, which has a rough surface, is formed throughout the surface areas of the front-end area part of the tapered part 46 and the small-diameter straight part 43, whereas the smooth surface part 48, which has a relatively smooth surface, is formed throughout the surface areas of the base-end area part of the tapered part 46 and the straight part 45. That is, the rough surface part 47 is formed at the front-end surface area of the punch 36, whereas the smooth surface part 48 is formed at a relatively base-end surface area thereof when viewed from the rough surface part 47. For example, the surface roughness Ra of the rough surface part 47 is 0.6 μm or greater. The surface roughness Ra of the smooth surface part 48 is less than 0.6 μm.

Next, an explanation is given below of a punching process (step) that is performed with the use of the pressing machine 30 that has the configuration explained above. In the same manner as in the foregoing first embodiment of the invention, as the punch 36 gradually makes its way deeper into the metal plate 31 from the front face 31 a thereof, the metal material of the front-face (31 a) part of the metal plate 31 and in the neighborhood thereof is pressed by the rough surface part 47 of the punch 36 and thus yields thereto so as to move in the arrowed direction K as drawn thereby. That is, the punch 36 moves deeper and deeper into the metal plate 31 while drawing the part of the metal material of the metal plate 31 in the arrowed direction K by the rough surface part 47 thereof. In addition, when the punch 36 makes its way in the metal plate 31, the smooth surface part 48 thereof smoothens the surface of the metal material that has been pressed away. Accordingly, the bulged part 49 only is formed on the reverse face 31 b of the metal plate 31 without forming any other bulged part around the punched area on the front face 31 a thereof (that is, no bump is formed at the punched front-face 31 a side). In addition, although the rugged shape of the rough surface part 47 is imprinted on the inner circumferential surface of the hole 40 that is now being formed in the metal plate 31 when the rough surface part 47 draws the part of the metal material of the metal plate 31 in the arrowed direction K, it is possible to ensure that the smooth surface part 48 smoothens the rugged pattern formed on the inner circumferential surface of the hole 40 thereafter. In this way, the hole 40 that has the same shape as that of the punch 36 is formed in the metal plate 31. Then, the bulged part 49 is removed in a grinding process. As a result, the hole 40 is formed into the nozzle opening 10, which is a through hole.

Next, with reference to FIGS. 10 and 11, an explanation is given below of the punch 36 of the pressing machine 30 according to a third embodiment of the invention. The punch 36 according to the present embodiment of the invention is characterized in that the rough surface part 47 is formed throughout the front-end-side area (denoted as E in FIG. 10) of the circumferential surface of the small-diameter straight part 43 and on the front-end plane of the small-diameter straight part 43. In addition, the punch 36 according to the present embodiment of the invention is characterized in that the smooth surface part 48 is formed at a base-end-side area of the circumferential surface of the small-diameter straight part 46 that is located relatively closer to the base end in comparison with the formation area of the front-end-side rough surface part 47 and at the surface area of the tapered part 46.

Next, an explanation is given below of a punching process (step) that is performed with the use of the pressing machine 30 that has the configuration explained above. The bottom dead point of the punch 36 according to the present embodiment of the invention has been set at such a position that the rough surface part 47 of the punch 36 passes through the metal plate 31 by a depth that is at least equal to the thickness of the metal plate 31 (where the plate thickness is denoted as D in FIG. 10) when the punch 36 is lowered to its bottom dead point. Specifically, the bottom dead point of the punch 36 according to the present embodiment of the invention has been set at such a position that a combined surface area (which is denoted as “d” in FIG. 10) that is made up of the rough surface part 47, which is formed in the small-diameter straight part 43 of the punch 36, and a front-end-side area part of the smooth surface part 48 formed therein passes through the plate thickness D of the metal plate 31. That is, the bottom dead point of the punch 36 according to the present embodiment of the invention has been set at such a position that, when the punch 36 is lowered to its bottom dead point, the combined surface area “d” that is made up of the rough surface part 47, which is formed in the small-diameter straight part 43 of the punch 36, and the front-end-side area part of the smooth surface part 48 formed therein overpasses (goes beyond) the reverse face 31 b of the metal plate 31.

First of all, the metal plate 31 that is made of 42 Alloy or the like is placed on the die 32 at a predetermined set position. Then, the punch 36 is lowered to the bottom dead point while the front end of the punch 36 is pressed against the metal plate 31 so as to make its way. As a result, as illustrated in FIG. 10, the combined surface area “d” that is made up of the rough surface part 47, which is formed in the small-diameter straight part 43 of the punch 36, and the front-end-side area part of the smooth surface part 48 formed therein passes through the plate thickness D of the metal plate 31. As a result, the hole 40 that has an imprinted shape corresponding to the shape of the punch 36 is formed in the metal plate 31. In this process, as the punch 36 makes its way, the metal material of the punched part of the metal plate 31 that is pressed and thus yields to the punching pressure of the punch 36 mainly moves (i.e., is drawn) toward the front-end side of the punch 36 in the direction K (i.e., plate thickness direction), which is indicated with an arrow in the drawing. As a result, the most part thereof bulges on the reverse face 31 b of the metal plate 31 so as to form a bump 49. On the other hand, even if the metal plate 31 is made of a relatively soft material such as 42 Alloy or the like, no bulged part is formed on the front face 31 a of the metal plate 31, which is the punched-side surface, unlike conventional art according to which a bulged part is formed also on the front face of a metal plate when a conventional punch (whose surface is not rough) is punched therein.

Specifically, as the punch 36 gradually makes its way deeper into the metal plate 31 from the front face 31 a thereof, the metal material of the front-face (31 a) part of the metal plate 31 and in the neighborhood thereof is pressed by the rough surface part 47 of the punch 36 and thus yields thereto so as to move in the arrowed direction K as drawn thereby. Although the rugged shape of the rough surface part 47 is imprinted on the inner circumferential surface of the hole 40 that is now being formed in the metal plate 31 when the rough surface part 47 draws the part of the metal material of the metal plate 31 in the arrowed direction K, it is possible to ensure that the smooth surface part 48 smoothens the rugged pattern formed on the inner circumferential surface of the hole 40 thereafter. More specifically, a pattern of streaks (impression) 50 is formed in the inner circumferential surface of the hole 40 at an area (which is denoted as “e” in FIG. 10, where e<d) corresponding to the area of the rough surface part 47 of the punch 36 that is positioned at the bottom dead point along the punching direction that is shown by the arrow K as the imprinted copy of the rugged shape of the rough surface part 47. In this way, the hole 40 that has the same shape as that of the punch 36 is formed in the metal plate 31. Then, the bulged part 49 is removed in a grinding process. As a result, the hole 40 is formed into the nozzle opening 10, that is, into a through hole. In addition, as a result of the grinding, the inner circumferential surface of the straight part 25 of the nozzle opening 10 is formed as a smooth surface in its entirety.

After the completion of the punching process, the metal plate 31 is demounted from the pressing machine 30 and then is subjected to the next bump removal process. In the bump removal process, the bulged part 49, which was formed during the punching process on the reverse face 31 b of the metal plate 31, is ground away. As illustrated in FIG. 11, the bump 49 is removed in this grinding process so as to form the hole 40 into the nozzle through hole 10. In addition, the metal plate 31 is polished so as to make the thickness thereof equal to a predetermined plate thickness. In this way, the pattern of streaks 50 that was formed in the inner circumferential surface of the hole 40 is removed when the bulged part 49 is ground away. As a result, it is possible to manufacture the nozzle plate 13 through which the nozzle openings 10 each having a smooth inner circumferential surface at the straight part 24 and a smooth inner circumferential surface at the tapered part 25 are formed.

As explained above, since the rough surface part 47 is formed throughout the front-end-side outer surface of the punch 36 of the pressing machine 30 according to the present embodiment of the invention whereas the smooth surface part 48 is formed at a base-end-side outer surface thereof that is located relatively closer to the base end in comparison with the formation area of the front-end-side rough surface part 47, as the punch 36 makes its way in the metal plate 31, the rough surface part 47 of the punch 36 causes the punched part of the metal plate 31 (metal material), which is pressed and thus yields to the punching pressure of the punch 36, to move (i.e., be drawn) in the direction K that is indicated with the arrow in the drawing. In addition, when the punch 36 makes its way in the metal plate 31, the smooth surface part 48 thereof smoothens the surface of the metal material that has been pressed away. Consequently, it is possible to ensure that the metal (material) escapes in the arrowed direction K in the punching process. That is, the punch 36 has a front-end-side part that draws the metal material of the metal plate 31 and a relatively-base-end-side part that smoothens the inner circumferential surface of the hole 40 at the base-end side. With such a structure, it is possible to avoid the formation of a bump at the peripheral edge of the hole 40 on the front face 31 a of the metal plate 31, thereby saving the trouble of removing the bump formed thereon, which is a necessary step according to conventional art. As a consequence thereof, it is possible to easily manufacture the metal plate 31 in which the minute holes 40 are formed as a result of presswork. In addition, it is possible to prevent the degree of circularity of the minute hole 40 from decreasing because a bump that was formed at the peripheral edge of the hole 40 on the front face 31 a of the metal plate 31 does not collapse and become deformed under the pressure applied by the pressing board 35.

Moreover, if the metal plate 31 that has been worked by the pressing machine 30 described above is mounted as the nozzle plate 13 of the recording head 1, it is possible to ensure that the inner circumferential surface of the straight part 25 of the nozzle opening 10 is formed as a smooth surface. Therefore, it is possible to achieve quick vibration of meniscus (i.e., the surface of ink at the opening side) of ink inside the nozzle opening 10. Thus, it is possible to achieve stable discharging performance for liquid drops that are ejected from the nozzle orifices 10.

In the configuration of the punch 36 of the pressing machine 30 according to the third embodiment of the present invention explained above, the rough surface part 47 is formed at the front-end-side area E of the outer surface of the small-diameter straight part 43. As illustrated in FIG. 12, the punch 36 of the pressing machine 30 according to a fourth embodiment of the present invention may be configured as follows. The rough surface part 47 is formed at the front-end-side area E of the outer surface of the small-diameter straight part 43 whereas the smooth surface part 48 is formed at a base-end-side area of the outer surface of the small-diameter straight part 43 that is located relatively closer to the base end in comparison with the formation area of the front-end-side rough surface part 47. In addition, another rough surface part 47′ is formed in a metal-contact surface area of the tapered part 46 that is brought into contact with the metal plate 31 when the punch 36 is punched into the metal plate 31 (which is denoted as E′ in FIG. 12).

Note that the present invention is not limited to the specific embodiments described above. That is, the invention may be modified into a variety of modes on the basis of the recitations of appended claims.

In each of the exemplary embodiments of the invention described above, the punch 36 includes the punch body part 45, the tapered part 46, and the small-diameter straight part 43. Notwithstanding the above, however, as illustrated in FIG. 13, the pressing machine 30 according to a fifth embodiment of the invention may be configured as follows. The pressing machine 30 according to the fifth embodiment of the invention is provided with a straight unit 55. A part of the straight unit 55 that is to be punched into a metal plate has a uniform diameter as viewed from the front end thereof. The rough surface part 47 is formed only at the front-end-side area of the circumferential surface of the straight unit 55. That is, it suffices if the rough surface part 47 is formed at least at a metal-contact area part of the outer surface of the punch 36 that is brought into contact with the metal plate 31 when the punch 36 is punched into the metal plate 31. With a rough surface part being formed at the front-end-side area of the circumferential surface of a straight unit as explained above, it is possible to use an existing punch just by working the outer surface of the existing punch so as to increase the surface roughness level thereof. As explained above, since the rough surface part 47 is formed only at the front-end-side area of the circumferential surface of the straight unit 55, it is possible to easily work the outer surface of an existing punch so as to increase the surface roughness level thereof and to use the worked existing punch.

In the configuration of the pressing machine 30 mentioned above, the nozzle opening 10 is formed through the metal plate 31 through the punching process and the bump removal process. Notwithstanding the above, however, in the configuration of the pressing machine 30 according to an exemplary embodiment of the invention, the metal plate 31 may be punched through with the use of the punch 36. That is, the bottom dead point of the punch 36 may be adjusted into a position that is further lower than the reverse face 31 b of the metal plate 31 so as to form a through hole in the metal plate 31 without performing the bump removal process.

Moreover, when the shape of the rough surface part 47 of the punch 36 is imprinted on the inner circumferential surface of the hole 40 of the metal plate 31 in the direction of the arrow K, during the process of surface treatment (a third step) of the inner circumferential surface of the hole 40, it is possible to make it easier to apply treatment liquid such as a repellent that repels ink that is ejected by the recording head and to perform the surface treatment easily.

In the configuration of the pressing machine 30 according to an exemplary embodiment of the invention, the nozzle plate 13 that is used in the recording head 1, which is a kind of a liquid spray head, is taken as an application example of the metal plate 31 in which the hole 40 is formed. Notwithstanding the above, however, the invention can be applied to the metal plate 31 that is used in other application.

In the foregoing explanation, the recording head 1 is taken as an example of a liquid spray head. Notwithstanding the foregoing, however, the invention is directed to various kinds of liquid spray heads; and therefore, the invention is also applicable to a variety of liquid spray heads that eject liquid other than ink. For example, the invention can be applied to a variety of recording heads such as an ink-jet recording head or the like that are used in an image recording apparatus such as a printer or the like, a color material ejection head that is used in the production of color filters for a liquid crystal display device or the like, an electrode material ejection head that is used for the electrode formation of an organic EL display device, an FED (field emission display), and the like, or a living organic material ejection head that is used for production of biochips. In addition, although the foregoing explanation is given while taking the recording head 1 as an example of a liquid spray head, it can be applied to a liquid spray apparatus that uses other liquid spray head explained above. 

1. A pressing apparatus that performs plastic working by pressing a punch into a metal material plate, the pressing apparatus comprising: a rough part that is formed at least at a front-end-side area of an outer surface of the punch that is brought into contact with the metal material plate, the level of surface roughness of the rough part being greater than that of other area part.
 2. The pressing apparatus according to claim 1, further comprising a smooth part that is formed at a base-end-side area that is located at a relatively base-end side in comparison with the area of the rough part, the smooth part being smoother than the rough part, wherein the diameter of the rough part is not larger than that of the smooth part.
 3. The pressing apparatus according to claim 1, the punch being inserted up to a point where the rough part goes beyond one surface of the metal material plate that is opposite to the other surface thereof that is provided at a side at which the insertion of the punch into the metal material plate is started.
 4. The pressing apparatus according to claim 3, the punch including a straight part that is uniform in outer diameter from the front end of the punch toward the base end thereof; and the rough part being formed at a front-end-side area of an outer surface of the straight part whereas the smooth part is formed at a base-end-side area that is located at a relatively base-end side in comparison with the area of the rough part.
 5. The pressing apparatus according to claim 4, the punch including a tapered part that is formed at a relatively base-end side in comparison with the area of the straight part; the diameter of the tapered part gradually increasing from the front-end side toward the base-end side; and the rough part being formed in the outer surface of the tapered part.
 6. The pressing apparatus according to claim 1, the rough part being pear-peel finished.
 7. A metal plate manufacturing method for manufacturing a metal plate by forming a hole as a result of pressing a punch into a metal material plate, the metal plate manufacturing method comprising: a first step of forming a hole by pressing, into the metal material plate, the punch that includes a rough part that is formed at least at a front-end-side area of an outer surface of the punch that is brought into contact with the metal material plate, the level of surface roughness of the rough part being greater than that of other area part.
 8. The metal plate manufacturing method according to claim 7, in the first step, the punch being inserted up to a point where the rough part goes beyond one surface of the metal material plate that is opposite to the other surface thereof that is provided at a side at which the insertion of the punch into the metal material plate is started.
 9. The metal plate manufacturing method according to claim 7, further comprising a second step of removing a bulged part that is formed around the hole formed in the first step on the one surface of the metal material plate that is opposite to the other surface thereof that is provided at the side at which the insertion of the punch into the metal material plate is started.
 10. The metal plate manufacturing method according to claim 7, further comprising a step of surface treatment.
 11. A method for manufacturing a liquid spray head, comprising: mounting a metal plate that has been worked by means of the metal plate manufacturing method according to claim 7, as a nozzle plate from the hole of which liquid is ejected.
 12. A method for manufacturing a liquid spray apparatus, comprising: mounting a liquid spray head that has been manufactured by the liquid spray head manufacturing method according to claim
 11. 